In troll fishing, it is desirable to maintain one's lure or bait at a constant depth, and to be able to repeat this depth one it is determined how deep the fish are located. It is also desirable that the fishing line descend from the boat at a steep angle, to minimize line drag and the chances of entangling the line with obstacles, other lines, and the like. While at trolling depth, the trolling device should maintain depth independent of boat speed, and should be stable; that is, it should not veer from side to side or vary in depth. Furthermore, it should not flutter or otherwise produce distracting noise or movement.
I am aware of prior U.S. patents disclosing devices in the nature of hydrodynamic plates designed to be towed through water by a boat. These devices are generally intended to maintain a bait or lure line at trolling depth; to do so, they may be constrained to have a certain angle of attack to the water. U.S. Pat. No. 2,645,053 provides a good exemplary prior art device, which trails behind the boat at an angle of about 15 degrees to horizontal.
To my knowledge, none of the many prior art proposals has achieved marked commercial success. The reason for this is a matter for conjecture; perhaps the prior devices lacked adequate stability or depth predictability, or perhaps they could not obtain sufficiently steep depression angles.
It is therefore an object of the invention to maintain a trolling line at a desired depth, which depth can be deduced from the trolling line length.
A second object is to obtain as large a line depression angle as possible.
Another object is to provide a simple trolling device having inherent hydrodynamic stability. A related object is to make trolling line depth independent of boat speed.
I have accordingly developed a new troll line depresser to control the running depth of a troll line. This device is capable of maintaining a line at a constant angle of from twenty-five to thrity degrees downward from the stern of a moving boat, whereby the bait depth can be determined merely by monitoring the line length. With my device, the line angle does not change with slight variances in speed, so that trolling depth is substantially speed-independent.